checkmate1996

Question,

My 79 has the upgraded 87 suspension package, (i.e. arms, spindles, brakes, etc). I am going to get the front end aligned to get ready for SITM (Mark, you may remember that problem!).

I am taking it to a place that has a hunter machine, so it will be done on the ground. But what should I tell him as far as alignment goes since I don't have a stock suspension or wheels. I'm assuming the numbers in the back of the manual for toe and camber won't be correct.

Thoughts?

SharkSkin

The numbers should still apply... why not?

AO

The reason why thay may be different is if the new spindles change the location of the wheels, then the trigonometry upon which the camber and toe are based will be off.

Now I don't know if the values have changed or not, but without diffinitive measuremetns, I would say the stock setting is about as good as it gets until you play around with it.

Ooohhh Why not compare the values between a '79 and an '87? Give me a sec....

Ok, I'm back. Look below and you will see the 79 on the right and the 87 on the left. Camber and caster are the same, and toe looks the same as well (although they give pressed and unpressed values.. not sure what that's all about). So I'd say, stick with stock, but keep an eye on the toe.

checkmate1996

Andrew, thanks for the post. Good stuff. I'll probably print it and hand it to the guy!

SharkSkin

I have the same diagram as you have on the right, in my tech specs booklet. What really cracks me up is the way that they have ride height measured to the center of the wheel. More precise in terms of locating the suspension at the correct angles -- but maybe just a bit impractical.

FlyingDog

I think they're saying you have to compensate for wheel diameter changes since they draw out 'b' and whatever letter that is (a?) from the center of the wheel to the floor.

SharkSkin

No, "b" is never called out in the tech spec book. Andrew posted pretty much the whole page, I have a higher resolution version on my tech specs page. Yes it's on the drawing... but is never assigned any meaning.

Garth S

I think that is the correct interpretation - although the WSM leaves it up to a ... "go figure it out yourself Bub" status - a theme often repeated.

..... the true suspension geometry is determined by the height differential between the reference point and the axle centerline - simply due to differences that effect the measured reference height (190-20mm) caused by tires of differing diameter/wear/inflation pressure/uneven floor/etc.. Using the reference point to the floor is the better way to establish this ... but the true reference is to the axle centerline.

The only alignment spec that I'm aware of havinging changed over the model years if the front caster. The spec increased from 3'30" (+30") to 4' (+30") .... and that was a retroactive change. ie - safe to increase caster on earlier cars, and recommended on later cars (S4 suspensions).
Translation .... you are safe to go up to 4.5 degrees caster - and some suspensions will not adjust to allow much less: the trick is to minimize the one with the higher value, and set the other side to match.

Rick Carter

Brad,
I'd liked to know your tire wear after 2-3 thousand miles. The best place Ron and I have found for accurate alignment is MAG in Columbus. Jeff is the service manager for Hi-Line (Porsche, Ferrari, Aston Martin, RR,Bentley, Lotus etc.) Service and very easy to work with.

checkmate1996

You guys will be the first to know. Brett Matthews had good experience with a gentlemen at Sears who uses a hunter machine. I believe the alighment is like ~100. If I remember correctly, MAG was quoting ~$250. If my tires die at 3K, I guess 250 is $$$ well spent!

SteveG

So it's Ohio and not Columbus, GA. I'll be passing thru there on the 28th. If you see a slate GTS on I-270 or east on 70 about 2 - 4 PM on 70, that's me.

checkmate1996

If you have a moment, stop by...I'll live right off of I270 ...just about a mile!

Fogey1

Andrew Olson wrote:
"... (although they give pressed and unpressed values.. not sure what that's all about). So I'd say, stick with stock, but keep an eye on the toe..."

_Maybe_ they're talking about settled and lifted and not settled.

As for measuring the ride height, I think the using the points on the suspension and measurement "d," which is given in the older publication, may be easier than trying to measure "#2."

SharkSkin

I don't see that... Not in the early tech spec book anyway, and the WSM simply calls out the distance from the check point on the suspension to the floor...

Strosek Ultra

Toe-in pressed and unpressed values is about using a spreader or presser bar to take up any slack in the front suspension and steering. The presser bar is used for MB cars but I have never heard of it when it comes to the 928. Attached images by Andrew Olsen are giving us specs for both toe-in unpressed and pressed. How do the professionals like Mr. Brown do it?
You will find the images in post #16.
Åke